The emphasis of research in this laboratory continues to be directed toward increasing our knowledge on the biology and biochemistry of the newly recognized human papovaviruses, BK and JC. Based on studies carried out in collaboration with Drs. Howley, Khoury, and Martin (LBV), a physical map of the BKV genome has been constructed. In addition, some information on JCV genome has been obtained and the extent and localization of common sequences between BKV, JCV, and the simian virus 40 (SV40) is now known. Since some of the early functions and gene products (T-antigens) appear to be shared between the human and simian papovaviruses, other studies were undertaken to study further the known early functions of the papovaviruses. Results of these investigations have shown that: (1) virus-specific transplantation antigens are not shared by the 3 viruses, (2) U-antigen is induced by SV40 and BKV, but not by JCV, (3) T-antigens induced by the 3 viruses are indistinguishable by fluorescent antibody or complement-fixation tests. Complementation studies have shown that BKV can provide the early functions defective at restrictive temperatures in tsA mutants of SV40, thus providing additional information on the relationship between the 2 viruses.